Does Paul's message reach unbelievers even though he writes to believers?
Yes, Paul's letters are addressed to believers, never to the unbelieving world, but his message inevitably reaches unbelievers as well. Writing to the predominantly Gentile church at Corinth, he communicates God's hidden wisdom, and that truth extends beyond the original believing audience to others who hear it.
Les teaches that Paul always writes to believers and never to the unbelieving world, but as he writes to believers, his message is going to go to the unbeliever, no doubt about it. In 1 Corinthians 2, Paul addresses the predominantly Gentile church at Corinth. Les notes that Paul uses the plural pronoun "our" rather than "my" because God knew this apostle would become a writer of Scripture. Paul speaks of the wisdom of God in a mystery, the hidden wisdom God ordained before the world unto our glory. The princes of this world did not know it; had they known, they would not have crucified the Lord of glory. Les also connects this to Peter in Acts 3, where Israel is given an escape route, though they were guilty of rejecting their Messiah.